Lipid Peroxidation and Antioxidant Mechanisms is a competitive renewal proposal for an NIEHS Program- Project that was funded in September of 2005. Environmental stress and lifestyle play an important role in diseases that contribute significantly to mortality in the U.S. Cigarette smoking, alcohol consumption and poor diet combine with other environmental factors to affect the incidence of several diseases. The formation of oxidants is a hallmark of many of these diseases and lipid peroxidation is a common result of diverse environmental insults. Indeed, oxidative stress has been closely associated with the onset of pathologies as diverse as cancer and cardiovascular disease. The underlying mechanisms linking environmental stresses with disease pathogenesis remain obscure. The studies proposed here will test the hypothesis that the balance of competing oxidation pathways for different lipid substrates governs adaptation to oxidative stress and oxidative injury. The Program Project also directly addresses the hypothesis that protein adduction by lipid peroxidation products alters cellular signaling and modulates diseases linked to oxidative stress. This Program Project includes four research projects and one scientific core facility in a tightly-knit group that will provide important insights into the role that oxidation and antioxidants play in human pathophysiology. Project 1 provides a mechanistic framework for understanding peroxidation profiles and leads the chemistry that provides novel lipid affinity-tags for studying protein-electrophile adducts. Project 2 explores the chemistry and biology of eicosapentaenoic acid (EPA), a fatty acid prominent in fish oil, and explores the hypothesis that EPA oxidation products may contribute significantly to the biological properties of this fatty acid. Project 3 evaluates electrophiles that play critical roles in cell signaling and provides the biological platform for studying lipid affinity tags in whole cells. Project 4 suggests that secondary electrophilic products of lipid peroxidation play critical roles in oxidant-associated molecular pathologies and explores methodologies for identification and analysis of protein adducts of these electrophiles. All of the projects are highly collaborative and are highly dependent on the Lipidomics Analysis scientific core.